Laser drilling refers to a laser machining procedure for forming a hole by heating a material with focused laser beams as a high-intensity heat source so as to melt or vaporize and then evaporate the material at a region irradiated by the laser beams. Currently, a CO2 continuous-wave (CW) laser beam is used in an existing laser drilling technique. FIG. 1 shows its operating principle, where a CO2 laser 1 outputs CW laser beams which are focused at a high temperature at a peripheral region on a substrate 2 where holes are desired to be drilled, so as to melt the material, thereby to drill the holes.
However, when the holes are drilled using the CO2 CW laser beams, some substrates, e.g., a glass substrate with ultrahigh chemical strength, are readily to crack, so the CO2 CW laser beams are mainly used for drilling holes in the glass substrate which is not chemically reinforced, rather than the glass substrate with ultrahigh chemical strength. In addition, generally the holes formed by the CO2 CW laser beams have poor surface quality, and a residual or dummy material cannot fall off from the substrate automatically.